1. Field of the Invention
This invention relates to direct heating surface combustors for gas turbines and, more particularly, to an improved combustor which provides low emissions.
2. Description of the Prior Art
Conventional gas turbine combustors generally have a primary combustion zone that provides burning at or near the stoichiometric fuel-air ratio. In a secondary zone following the primary zone excess air is utilized as a diluent to achieve the desired turbine inlet temperature. Products of combustion produced by such combustors contain relatively high quantities of the oxides of nitrogen (NO.sub.x) because the primary flame is nearly adiabatic and the temperatures utilized are high. With the growing interest in control of our pollution such NO.sub.x emissions are becoming increasingly unacceptable.
Examples of essentially adiabatic combustors which provide cooling through the use of injected air, water or exhaust gases are found in U.S. Pat. Nos. 3,088,280; 3,541,790 and 3,440,818. U.S. Pat. No. 3,322,179 discloses a radiant surface combustor of general interest.